How to debug Deno in VSCode

Question

How do we configure .vscode/launch.json to debug Deno projects?

The IntelliSense the VSCode provides when I was in configurations didn't offer an option for Deno. Or is there an extension for this?

Cleave

Answer 1

You need to attach the debugger, as per the deno manual.

Create .vscode/launch.json replacing <entry_point> with your actual script and then F5.

{
    "version": "0.2.0",
    "configurations": [
        {
            "name": "Deno",
            "type": "node",
            "request": "launch",
            "cwd": "${workspaceFolder}",
            "runtimeExecutable": "deno",
            "runtimeArgs": ["run", "--inspect-brk", "-A", "<entry_point>"],
            "port": 9229
        }
    ]
}

It will stop at the breakpoints you set on VS Code, tried here and it worked fine.

About the VS Code plugin:

Official support in plugin is being worked on - https://github.com/denoland/vscode_deno/issues/12

Tarver

Upvoted. I also had to add "outputCapture": "std" to see logs in the debug console. – Rhonda

after spending hours on github and google, this worked in a second. Note: had to add "outputCapture": "std" for console logs. thanks @Rhonda – Strew

The link to the deno manual seems to be dead. – Scalawag

@Scalawag it did in fact changed. I updated in the answer, thanks for pointing that out. – Tarver

The debugging will not work with this configuration. You also need to set "debug.javascript.usePreview": false in your settings because github.com/denoland/vscode_deno/issues/… – Helpful

And now that the preview has become the default, that setting is useless again, and Deno breakpoints don't work yet again. No idea how to fix it. – Helpful

All this worked for me, but I needed to change "port" to "attachSimplePort" as described elsewhere. – Sihon

why is it "type": "node" but not "type": "deno"? Is it that I have to install node before deno to run the debug? – Galsworthy

Answer 2

The official VS Code Deno extension comes with handy debug support starting with v2.3.0.

Screencast from the PR:

Fresh projects

You can already press F5 to debug the active file without launch.json (quite useful).

To auto-generate launch.json with a Deno entry: Press CTRL+Shift+D (Open debug view) → "create a launch.json file" → Deno

Add Deno entry in existing launch.json

Press Add Configuration... in opened launch.json (see screencast above). F5 will now trigger the currently active debug launch action.

Launch active file

To debug the currently active file in case of an already configured launch.json, change:

{
  "type": "pwa-node",
  "program": "${file}", // change "program" value to "${file}"
  // ...
},

Create debug selection shortcut

// Inside keybindings.json
{
    "key": "ctrl+alt+d",
    "command": "workbench.action.debug.selectandstart",
    "args": "Start debug task"
},

The shortcut is called "Debug: Select and Start Debugging" - see also this related post.

Enable log output in Debug Console

To have log output shown in the debug console, I still needed to add "outputCapture": "std" to the config entry. More infos:

• Where is stdout for VS Code?
• Debug output doesn't appear in debug console without "outputCapture": "std" #41600

Related

• https://code.visualstudio.com/docs/editor/debugging
• https://code.visualstudio.com/docs/nodejs/nodejs-debugging

Rhonda

Deno launch configuration template seems to have been (temporarily?) removed again, as you need to insert it manually now – Helpful

This needs upvotes. This answer made me restart and F5 indeed works out of the box. After which I auto-generated the launch.json like ford04 suggested and just added outputCapture and the whole thing worked. – Rehash

Answer 3

to debug current file, you can use below configuration :)

"outputCapture": "std" allows deno to print to VS code console

{
    "version": "0.2.0",
    "configurations": [
        {
            "name": "Deno",
            "type": "node",
            "request": "launch",
            "cwd": "${workspaceFolder}",
            "runtimeExecutable": "deno",
            "runtimeArgs": ["run", "--inspect-brk", "-A", "${fileBasename}"],
            "outputCapture": "std",
            "port": 9229
        }
    ]
}

P.S. just added to Evandro Pomatti's answer

Gregoor

that's pretty handy – Tarver

Answer 4

I had to replace port with attachSimplePort

{
    "name": "Deno",
    "type": "node",
    "request": "launch",
    "cwd": "${workspaceFolder}",
    "runtimeExecutable": "deno",
    "runtimeArgs": ["run", "--inspect-brk", "-A", "${fileBasename}"],
    "outputCapture": "std",
    "attachSimplePort": 9229
},

Gaekwar

Answer 5

Install the official Deno extension, Then generate a configuration by opening the Run and Debug panel, selecting Create a launch.json file, and choosing the Deno option from the debugger options.

Amphitheater